This invention relates to a lubricating device for a four stroke outboard motor and more particularly to an improved lubricant system for such an outboard motor.
It has been proposed to employ four cycle engines as the power plant for an outboard motor. Although two cycle engines are normally employed for this purpose because of their simplicity and high power output to displacement, there are some instances when it may be desirable to employ a four cycle engine as the power plant in an outboard motor. However, a four cycle engine requires a closed lubricating system that includes a lubricant reservoir and an arrangement for circulating the lubricant through the engine for its lubrication and then returning it to the lubricant reservoir. Also, it is desirable to provide some form of strainer or filter assembly for the lubricant. Due to the compact nature of an outboard motor, it has been relatively difficult to provide an adequate lubricant supply for a four cycle powered outboard motor. This is primarily due to the fact that outboard motors frequently are run for long periods of time at full throttle and, therefore, it is desirable if not essential to provide a relatively large lubricant capacity.
It has been proposed to provide a lubricant reservoir for an outboard motor having a four cycle engine in which the lubricant reservoir depends into and is contained primarily within the drive shaft housing. Although such an arrangement will permit the use of a large lubricant reservoir, normally it is the practice to provide a large expansion chamber for silencing the exhaust gases also in the drive shaft housing. Therefore, as the size of the lubricant reservoir is increased, the possible size of the expansion chamber for the exhaust system is decreased.
It is, therefore, a principal object of this invention to provide an improved arrangement wherein an outboard motor may be powered by a four cycle internal combustion engine having a large lubricant reservoir and wherein the lubricant reservoir does not depend into the drive shaft housing to any significant extent.
It is a further object of this invention to provide an improved four cycle powered outboard motor having a dry sump lubrication system wherein the dry sump is positioned externally of the engine and of the drive shaft housing and lower unit